Variable time delay control structure for channel matching

Abstract

A cosite interference cancellation system is provided for improved rejection of a signal coupled from a transmission antenna into a local receive antenna in the presence of local multipath. The cosite interference cancellation system and associated method advantageously provide improved signal rejection by continuously controlling (adjusting) a matching time delay to reduce cosite interference.

What is claimed is: 
     
       1. An interference cancellation system, comprising:
 (A) a variable delay line ( 19 ) for adjusting a signal propagation time of a sampled transmission signal ( 40 ) propagated through a controlled propagation path, the variable delay line ( 19 ) comprising a delay having an adjustment range to compensate for delay differences in the sampled signal path and an uncontrolled propagation path, the delay comprising:
 at least one fixed delay element; and 
 a variable delay element continuously varying a delay of sampled transmission signal to implement a match between the sampled transmission signal and a propagated received signal propagated through the uncontrolled propagation path yielding a delayed coupled signal; 
 
 (B) an adaptive time delay control (ATDC) module ( 10 ) for receiving the sampled transmission signal and the propagated received signal, delaying the sampled transmission signal and the propagated received signal, generating a first autocorrelation value from the sampled transmission signal and the delayed propagated received signal, generating a second autocorrelation value from the delayed sampled transmission signal and the delayed propagated received signal, and continuously calculating a delay based on the first and second autocorrelation values to be added to the controlled propagation path through the variable delay element to achieve a match of the sampled transmission signal passing through the controlled propagation path with the propagated received signal passing through the uncontrolled propagation path; and 
 (C) an adaptive control loop ( 6 ) for adjusting a complex weighting of the delayed coupled signal ( 57 ) to maximally cancel the sampled transmission signal received in the propagated received signal ( 30 ). 
 
     
     
       2. The interference cancellation system of  claim 1 , wherein the variable delay line ( 19 ) is a voltage controlled delay line. 
     
     
       3. The interference cancellation system of  claim 1 , wherein the variable delay line ( 19 ) is a digitally controlled delay line. 
     
     
       4. The interference cancellation system of  claim 1 , wherein the adaptive time delay control (ATDC) module ( 10 ) is configured to provide continuous, non-interrupting, adjustment of the variable delay line ( 19 ). 
     
     
       5. The interference cancellation system of  claim 1 ,
 wherein the adaptive control loop ( 6 ) is configured to adjust only phase and amplitude of the delayed sampled signal to cancel coupled received signal in the propagated path, and 
 wherein the ATDC is configured to adjust the delay to achieve the match between the sampled transmission signal and the propagated received signal. 
 
     
     
       6. The interference cancellation system of  claim 1 ,
 wherein the adaptive control loop ( 6 ) adjusts only phase and amplitude of the delayed sampled signal to cancel coupled received signal in the propagated path, 
 wherein the phase and amplitude adjustment is implemented by In-phase and Quadrature weighting, and 
 wherein the ATDC is configured to adjust the delay to achieve the match between the sampled transmission signal and the propagated received signal.